When it comes to fraud, few things are more frowned upon than tampering with the food supply. That’s true today and it was true in centuries past. In fact, during the medieval era, there was a particular preoccupation with the idea that bakers were tampering with food and/or short-changing their customers.

While there wasn’t much that bakers could do to fight rumors they were substituting cheaper ingredients for flour in their bread or finding other ways to cheat their customers, there was one thing they could do to avoid being fined for underselling their bread: give some away.

This is where the term “baker’s dozen” comes from in reference to 13 items (instead of the usual 12 one finds in a dozen). To avoid being fined or jailed for short-changing customers, medieval bakers would simply give patrons who ordered a dozen loaves thirteen of them—then if any or all of the loaves were slightly underweight, then the bonus loaf would make up the difference.